An internal combustion engine equipped with a compression release mechanism (or decompressor) that connects the combustion chamber with an intake passage and/or an exhaust passage during a compression stroke is commonly known. According to such a compression release mechanism, in-cylinder pressure is released during startup or when coasting with the fuel cut off, thereby reducing the load on the startup motor during startup, and also suppressing deceleration shock when starting coasting with the fuel cut off.
One type of compression release mechanism controls the lift amount of an intake valve and/or an exhaust valve, so as to put the intake valve and/or the exhaust valve into a constant open state at least during the compression stroke. Another type of compression release mechanism is equipped with a dedicated valve for selectively putting the combustion chamber and the exhaust passage into a communicating (open) state or a non-communicating (closed) state.
With the device disclosed in Patent Literature 1, while coasting with the fuel cut off, if at least a predetermined degree of deceleration is conducted and the battery is not fully charged, an intake valve and an exhaust valve are fully opened by the compression release mechanism, thereby causing the combustion chamber to communicate with the intake passage and the exhaust passage during the compression stroke, and conducting electric power regeneration. According to this configuration, deceleration shock caused by engine deceleration torque during braking operation may be decreased, and additionally, engine power losses (i.e. pumping losses) may be reduced to facilitate electric power regeneration.